coaxialcylinder
A coaxial cylinder refers to one of two or more cylindrical surfaces or solids that share a common central axis. The simplest configuration is a pair of concentric cylinders, an inner cylinder of radius a and an outer cylindrical shell of radius b, often described as a cylindrical shell or annular cylinder when considering the region between radii. Coaxial cylinders are a basic geometric and engineering object used in mechanics, electromagnetism, fluid flow, heat transfer, and structural design.
Geometric and physical properties are frequently expressed per unit length for infinitely long or slender models.
Applications include coaxial cables (transmission lines with concentric conductors), pipe-within-pipe heat exchangers, bearings and journal assemblies,